This invention relates to vacuum operated waste disposal systems used on passenger vehicles, in particular railcars.
The main components of such a waste disposal system are a toilet assembly comprising a flush valve assembly, a toilet bowl, a spray ring, a support base, a flush control unit; and a waste tank assembly comprising a waste holding tank with compression load cells in communication with the toilet bowl through a drain line. A preferred embodiment of a toilet assembly is described and claimed in a copending application, incorporated herein by reference, U.S. patent application Ser. No. 07/862,518, issued as U.S. Pat. No. 5,271,105. filed on same date as the present invention and assigned to the Assignee of the present invention.
Prior art vacuum-operated waste tank assemblies for railcars are considered either recirculating, partial retention or full retention. Prior art recirculating assemblies do not contain a waste tank downstream to collect the waste. These prior art recirculating assemblies contain a number of disadvantages in that due to the lack of a waste tank, the prior art recirculating assemblies are very complex, requiring numerous pumps, valves, filtration units, and means for deodorizing and sanitizing the liquid waste used as the recirculating flushing fluid.
Prior art partial retention waste tank assemblies for railcars utilize a small partial retention waste tank which has the disadvantage of not being capable of retaining the waste material throughout the entire transit of the railcar. Once the prior art partial retention waste tank becomes filled, the waste is dumped out of the tank and into the environment during the course of the transit. These prior art partial retention waste tanks have the additional disadvantage of not being a fully enclosed system. These prior art partial retention waste tanks do not have the means to maintain a constant vacuum throughout the system even when the vacuum blower is not operative. This prevents the valve member, which selectively connects the bowl to the waste tank, from sealing the waste tank assembly from the toilet assembly. Thus, in partial retention systems, the foul odor from the waste tank is permitted to enter the lavatory.
The prior art full retention waste tank assemblies utilize a permanent waste tank capable of retaining the waste throughout the entire length of the transit. However, when prior art full retention waste tanks have been utilized, they have proven to cause a serious problem in use since they do not accurately measure waste collected in the interior of the tank. Thus, waste entering these prior art full retention waste tanks tends to explode and cake onto the outer surface of the waste level sensors. As a result, false readings or total waste level sensor failure is the result.